addCompass {PBSmapping} | R Documentation |
Add a compass rose to an existing map, similar to those found on nautical charts showing both true north and magnetic north.
addCompass(X, Y, rot="magN", cex=1, col.compass=c("gainsboro","blue","yellow","black"), ...)
X |
Longitude coordinate (degrees N) for centroid of compass rose. |
Y |
Latitude coordinate (degrees W) for centroid of compass rose. |
rot |
Rotation (degrees) counterclockwise from 0 degrees (true North). See Details. |
cex |
Character expansion to use in the display. |
col.compass |
Colours for compass rose components (in order): |
... |
Additional parameters to pass to the |
The basic idea comes from Jim Lemon (see References), but is modified here to reflect a compass rose used on BC nautical charts.
The default rotation ("magN"
) is a calculation of the initial
bearing of a great-circle arc from the compass position to the north
geomagnetic pole using the function calcGCdist
.
No valule returned.
Rowan Haigh, Program Head – Offshore Rockfish
Pacific Biological Station (PBS), Fisheries & Oceans Canada (DFO), Nanaimo BC
opus locus: Institute of Ocean Sciences (IOS), Sidney BC
Last modified Rd: 2016-04-04
[R-sig-Geo] How to display a compass rose on a map
Magnetic North, Geomagnetic and Magnetic Poles
addBubbles
,
addLabels
,
addPoints
,
addStipples
,
calcGCdist
local(envir=.PBSmapEnv,expr={ data(nepacLL,envir=.PBSmapEnv) par(mfrow=c(1,1),mar=c(3,4,0.5,0.5)) plotMap(nepacLL, xlim=c(-134.5,-124.5), ylim=c(48,55), plt=NULL, col="lightyellow", cex.axis=1.2, cex.lab=1.5) addCompass(-132, 49.5, cex=1.5) })